{ "data": { "question": { "questionId": "1510", "questionFrontendId": "1394", "boundTopicId": null, "title": "Find Lucky Integer in an Array", "titleSlug": "find-lucky-integer-in-an-array", "content": "

Given an array of integers arr, a lucky integer is an integer that has a frequency in the array equal to its value.

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Return the largest lucky integer in the array. If there is no lucky integer return -1.

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Example 1:

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\nInput: arr = [2,2,3,4]\nOutput: 2\nExplanation: The only lucky number in the array is 2 because frequency[2] == 2.\n
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Example 2:

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\nInput: arr = [1,2,2,3,3,3]\nOutput: 3\nExplanation: 1, 2 and 3 are all lucky numbers, return the largest of them.\n
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Example 3:

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\nInput: arr = [2,2,2,3,3]\nOutput: -1\nExplanation: There are no lucky numbers in the array.\n
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Constraints:

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